Even though current technologies of fiber laser have made significant progress toward achieving a compact and reliable fiber laser system providing high quality output laser with ever increasing output energy, however those of ordinary skill in the art are still confronted with technical limitations and difficulties. Specifically, in a fiber laser system implemented with the Chirped Pulse Amplification (CPA) for short pulse high power laser amplifier, the CPA systems are still limited by the technical difficulties that the third order dispersion (TOD) limits the scalability of the laser systems. Such limitations were not addressed in the conventional technologies due to the fact that the conventional solid-state laser utilizes Grating-Lens combination and Treacy compressor for pulse stretching and compressing. Ideally, in such solid-state systems, all orders of dispersion can be compensated, but the material dispersion can distort and damage this ideal situation. But the material dispersion is not a serious problem in solid-state laser system because the material dispersion is generally considered as not important. However, for a fiber laser system, the situation is different due to the fact that in the fiber laser systems, attempts are made by using the fiber stretcher to replace the grating-lens combination for the purpose of significantly increasing the system reliability. However, the TOD limits the ability for de-chirping when using Treacy compressor since both fiber stretcher and Treacy compressor have positive TOD even this combination can remove the second order dispersion completely. This issue of TOD dispersion makes it more difficult to develop a high-energy fiber laser amplifier with <200 fs pulse width. Actually, the technical difficulty of TOD dispersion is even more pronounced for laser system of higher energy. A laser system of higher energy requires a higher stretch ratio and that leads to a higher TOD. Therefore, for laser system of higher energy, it is even more difficult to re-compress the pulse to the original pulse width. For fiber laser running below 1.3 μm, e.g., Yb fiber laser, the conventional fiber CPA laser uses normal dispersion (grating-lens or fiber stretcher) for pulse chirping and abnormal dispersion, e.g., the grating pair or Photonic Band-gap (PBG) fiber, for pulse de-chirping. However, such systems still encounter technical difficulties in recompress the pulse width. Furthermore, the commercially available PBG fibers are too lossy, e.g., 0.1˜0.2 dB/m. The splicing loss between the PBG fiber and the single mode fiber is 1 to 2 dB that may lead to a total loss as large as 10 dB when the PGB fiber is placed after the amplification chain. On the other hand, PBG fiber has a center hole, when it is spliced with silica core, the reflection from the splice will largely affect the performance of the amplification chain.
Therefore, a need still exists in the art of fiber laser design and manufacture to provide a new and improved configuration and method to provide fiber laser to compensate the dispersion generated in the laser system due to the TOD effects such that the above-discussed difficulty may be resolved.